February 13, 06-30 hr isentropic pressure, wind and local pressure derivative

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February 13, 06-30 hr isentropic pressure, wind and local pressure derivative

Notes:

This loop shows NAM forecasts of pressure, wind and the local pressure derivative (shaded) on the 295 degree K surface. The strong low-level jet was associated with very strong adiabatic pressure advection (“isentropic lift”), indicating warm advection and forcing for upward motion. The forcing associated with the advancing mid-level wave can be implied from the local pressure derivative. Blue shading corresponds to negative values, while green shading correspond to positive values, or forcing for upward motion due to the approach of the wave. In this case, the isentropic lift became juxtaposed with forcing for upward motion due to the approach of the wave during the afternoon on the 14th (positive pressure advection was juxtaposed with green shading). The highest snowfall rates were observed during that time.